Centralized traffic control system for the code control of interlocked switches and signals



Sept. 16, 1952 F. T. PAscoE ET Al. 2,6m074 CENTRALIZED TRAFFIC CONTROL SYSTEM FOR THE CODE CONTROL OF' INTERLOCKED SWITCHES AND SIGNALS INVENTORS. Fraai: IIPawfoe and y 6A/@Poma Sept. i6, E952 F. T. PAscoE ET AL CENTRALIZED TRAFFIC CONTROL SYSTEM FOR THE CODE CONTROL OF' INTERLOCKED SWITCHES AND SIGNALS l0 Sheets-Sheet 2 Filed June 2. 1947 E I INENTORS Frank Zareaefmd @www CSQ@ WM Sept 16, l952 F. T. PAscoE ET AL 2,611,074

CENTRALIZED TRAFFIC CONTROL SYSTEM FOR THE CODE CONTROL OF INTERLOCKED SWITCHES AND SIGNALS Filed June 2, 1947 l0 Sheets-Sheet 5 E/ cons coNTRoLLEo /k'lj 1i/WK; 10959 F15 JC'.

y INVENTORS. Frank TiPayeoe md THEIR Arma/mf.

Sept. 16, 1952 F. T. PAscoE ET AL 2,611,074

CENTRALIZED TRAFFIC CONTROL SYSTEM FOR THE CODE CONTROL oF INTERLOCKED SWITCHES AND srsNALs 10 Sheets-Sheet 4 Filed June 2, 1947 a d Z J v., m y MV w mi mw? 0 5 -I z www d m m @d m wa wa ma fsmd @d m d M m c 6 a 6 Z y y @y L uw L q L i f a D .a Sg .w 4b I D W fr MMM ad. 5%? Smm .L W4 M 6% Wj F D I iIIV Mlv Wm F73 7 l|||l| ||||I|| ll lllllllllll Il lll llllllllll 7 b ab a b K la f K mh D @N @N C s U -m ,aw -lel lllll-- 2` 2 K K nw mi M e A@ L U THEIR Anm/vnf.

SePf- 15, 1952 F. T. PAscoE ET Al. 2,511,074

CENTRALIZED TRAFFIC CONTROL SYSTEM FOR THE CODE CONTROL OF' INTERLOCKED SWITCHES AND SIGNALS Filed June 2, 1947 l0 Sheets-Sheet 5 SW W? 2349713 z@ an if ZIPR 55W -J`V 3 @1:12312 F aV B, I6 b INVENToRs'.

Frank II Parco@ and BY Ap L.Jep0me.

IHEJ!! ATTORNEY Sept. 16, 1952 F. T. PAscoE ET AL 2,611,074

CENTRALIZED TRAFFIC CONTROL SYSTEM FOR THE CODE CONTROL OF INTERLOCKED SWITCHES AND SIGNLS Sept' 16 1952 F. 1'. PAscoE ETAL 2,611,074

CENTRALIZED TRAFFIC CONTROL SYSTEM FOR THE CODE CONTROL OF INTERLOCKED SWITCHES AND SIGNALS Y Filed June 2, 1947 10 Sheets-Sheet 7 WWP Wp ZIM;V

l 62H @HH @im a I g E6 l EL ffm/P ma Mm 0 e INVENTUM'. Frank 1T Parco@ and u I Aff LJl 't W im@ P 2a ,BY i @me 16, 1952 F. T. PAscoE ETAL 2,611,074

CENTRALIZED TRAFFIC CONTROL SYSTEM FOR THE CDE CONTROL oF INTERLocxED SWITCHES ANDSIGNALS Filed June 2, 1947 1o sheets-sheet@ coNTRoLLEo CONTROLLED BY CIRCUITS CORRESPONDING T0 CIRCUITS CORRESPONDING TO CIRCUIT FOR l WZ Sept 15, 1952 F. T. PAscoE ET AL 2,611,074

CENTRALIZED TRAFFIC CONTROL SYSTEM FOR THE CODE CONTROL OF INTERLCKED SWITCHES AND SIGNALS Filed June 2, 1947 10 Sheets-Sheet 9 WSH gh/Z [WASH V 56M :m1/P 3W/p 54S f-LWZJ'INWP IRWP" 15M IWZ D if l. if.. ,j El@ i5 ,3., WP I g 6 [IMD i l I l I I H 1 -m l ...-4 zVWP 53W il 7AM/P 712W? 5 coNTRoLLED BY clRculTs coNTRoLLEo BY clRculTs coRREsPoNDlNG To clRculTs Fly. CORRESPONNNG To |RU|TS FoR aNwP and sRwP Fo INwP and mwP.

7m ZMS 434s 6R45 /Z INM 234s ld' APPROACH coNTRoLLED ZIZH CONTROLLED BY CIRCUITS CORRESPONDING TO CIRCUIT` CONTROLLED BY CIRCUlT FoR aLAs. F2 O cinazsgrnme To cmculT W5 gm WS @my .me 555 5W; 5m 7W; @Ms

b bg@ .ff gnb 15's 7h55 23.45 im 7TH ZMS c @n Vga I-Eqc p5 Fig. ZH.

c c d IN VEN TORJ'. Fmr/2li T M009 and THEM ATToRNEY,

Sept. 16, 1952 F. T. PAscoE ET AL 2,611,074

CENTRALIZED TRAFFIC CONTROL SYSTEM FOR THE CODE CONTROL OF INTERLOCKED SWITCHES AND ,SIGNALS Filed June 2, 1947 l0 Sheets-Sheet lO cone coDF EcoNTRoLLED l oNTRoLLED 10%? M i I ZNWP `@VW z"*-f 1. d" 5 i Lgs l 43H5 f- -l l l l 112241? Z I v 1 /11p l 1 1?; :5 B

T ZIP @f4-5;( coDE coNTRoLLED 5TH IIHWP PW ,'166 .Je l 11V 51's i? ma ma I l i l l J 5 'e 5: i a I l E l 1 *j Vf 375A; '-HQB: I l I t ic l E i I maia TP g l i b a i y e 1 ilZ E 11545 f i616? l :coDEcoNrRoLLEp I 752721 53W 'WWP d f ld 16ms @wmv/1': -HB

1Y0/'40 ITP :HR

I V ITS.' 7 b /EC 'J I CODE CONTROLL; la 'h I :3 lb b I I INVENToRs la Fmnlz/ fPas'cae and By r l. Jepome. izq. ZK

' 7mm www Patented Sept. 16, 1.952f

CENTRALIZED TRAFFIC CONTROL SYSTEM FOR THE CODE CONTROL OF INTER- LOCKED SWITCHES AND SIGNALS Frank T. Pascoe, Carnegie, and Arthur L. Jerome, Edgewood, Pa., assignors to Westinghouse Air Brake Company, a corporation of Pennsylvania Application June 2, 1947, Serial No. 751,908

5 claims. l

Our invention relates to centralized trafliccontrol systems for railroads, and more particularly,

to railway traiiic controlling apparatus for the control of electrically interlocked track switches and railway signals from a control office.

Our invention is particularly adapted for use in connection with a selective communication system of the code type, such, for example, as the remote control system shown in Letters Patent of the United States No. 2,229,249, issued January 21, 1941, to Lloyd V. Lewis, and in its specific embodiment as disclosed herein, our invention is illustrated as arranged for use in the system of this patent.

In remote control systems of this type, the components are assembled in the form of individual storagerunits each identied by a selective code call. Each storage unit in the eld is adapted to control and indicate a plurality of traine governing devices, such as power operated track switches or the railway signals which govern tran-lc movements over the switches, and is linked, by means of its code call, with a corresponding storage unit in the oiiice control machine which governs the transmission of control codes for effecting the operation of the switches or signals in accordance with the positions of their control levers. Each control code is initiated by pressing an individual starting button associated with the control levers of the corresponding group, or by other suitable means, and includes in addition to the code call a group of code elements reflecting the position of each of the levers of the group.

` Each office storage unit also includes a group of indication stick relays which respond to indicationcodes transmitted by the station storage unit having the same code call, to indicate selected conditions in the iield. Furthermore, the system is arranged to 'transmit the'codes one at a time over a single line circuit, without interference, codes originating at the same time, or while the line circuit is in use, being transmitted one at a time in a given order of code superiority.

:In the application of the remote control system to the control of trafiic on single track railroads, where generaly each station includes only one track switch, the preferred mode of operation is to include in the samecontrol code elements for changing the position of the switch and for clearing a signal which governs train movements over the switch. On the other hand, in the application of the system to interlocked track layouts including a plurality of track switches, it is sometimes preferred to delay the transmission ofthe signal clearing code until indications have been received that each switch of the route has assumed the desired position.

In interlocked track layouts having a plurality of track switches establishment of a route may involve movement of more than one track switch.

If movement of each track switch necessitates'y transmission of a separate control and indication code, a large number of such codes will be required, and preparation of routes through the track layout maybe delayed because of delay in the transmission of the control and indication codes. Y

The system of our invention is of the type in which the control apparatus at the oilice is so arranged that any route through a track layout involving one or more track switches may be set up by positioning the switch levers to indicate the route desired, reversing the signal lever for the entering signal, and then pressing the starting button associated with the operated signal lever. If preferred, the signal levers may be of the pushturn type so that each signal lever incorporates a starting button which may be operated during movement of the lever. If the signal levers incorporate thestarting buttons, it is preferred to have the levers arranged so that the levers may be moved without operating the starting buttons. and so that the starting buttons may be operated without moving the levers.

Each signal starting button when depressed always establishes a circuit for energizing the starting relay for the storage unit controlling the signal with which the starting button is associated.r Each signal starting button when depressed may also establish circuits for energizing the starting relay or relays for one or more additional storage units controlling the track switches so that all of the control codes nesssary to establish a complete route are initiated by pressing of a single starting button, Each of the circuits governed by a signal starting button iorenergizing a starting relay for an additional storage unit is automatically controlled so as to be established only when the route set up requires transmission of a control code by the additional storage unit, thereby to insure transmission of all essential control codes and at the same time prevent transmission of unnecessary control codes.

Thus it follows that in case the establishment of the desired route requires the operation of a switch and of a signal, the pressing of the appropriate starting button for the signal lever not only initiates, or stores for transmission, a signal clearing code, as heretofore, but also initiates the transmission 0f another code for operating the switch, the transmission of which precedes that of the signal clearing code. The equipment is arranged so that the transmission of the signal clearing code is delayed until an indication code is received which indicates that the switch occupies the position designated by the controlling switch lever, whereupon the signal control code is automatically transmitted without further effort on the part of the operator.

The system is arranged so that the operation of only one starting button is required to establish a route, even though the transmission of several different control codes is required in order to se.. up the route, and each switch operating code is initiated only when the switch control lever is out of correspondence with the indicated position of the switch, thereby avoiding the transmission of idle codes containing control elements for switches which already occupy the required positions.

A feature of our invention is that the control and indication of all of the, track switches in a layout is concentrated in a minimum number of storage units whereby to enable any route through the layout to be established with a minimum number of codes.

One object attained byV our invention is the, provision of improved means for insuring that the code for clearing the signal will be the last of the series of route establishing codes to be transmitted, regardless of the order of superiority of the different codes. In this respect this invention is an improvement upon that disclosed in an application for Letters Patent of the United States, Serial No. 649,598, led February 23, 1946, by Arthur L. Jerome, Lloyd V. Lewis and Frank T. Pascoe, for Centralized Traffic Control Systems of the Code Type for the Control of Interlocked Track Switches and Railway Signals, and is similar to that disclosed in an application for Letters Patent of the United States, Serial No. 708,920, led byV us on November 9, 1945, now Patent No. 2,576,038, granted November 20, 1951, for Centralized Traific Control System for the Code Control of Interlocked Switches and Signals.

The principal feature of this invention is the provision of improved means for selectively controlling each of a plurality of signals through a single storage unit.

A further featureof this invention is the provision of improved means of the type described which is arranged so that the transmission oi4 the control code for clearing each of a plurality of signals governed through a storage unit is automatically initiated when the route governed by the signal is indicated to be complete, and so that the control code governing each signal neither interferes with nor is interfered with by the'control code for governing other signals controlled through the same storage unit.

Another feature of the invention is the provision, in a system of the type described in which a route relay at the oifice is locked energized when a control code for clearing the associated signal is transmitted, of improved means at the iield location which operates in such a manner that as soon as a control code is received at a field station to clear a signal, the circuits governing transmission of indication codes for showing the condition of this signal are controlled to insure that either the "signal clear or approach locked indication will be transmitted to the office. whereby to prevent premature release of the route locking relay at the oiice.

Another object of this invention is to provide improved means for selectively governing a plurality of functions through a single eld station in such a manner that while control of any one of the functions may be initiated at any time, the transmission of the control code for each function is deferred until predetermined conditions exist, whereupon the code is automatically transmitted, the equipment being arranged so that transmission of the control code for performing one function does not interfere with the storage of the control code for another function.

A further object of this invention is to provide improved means of the type described which isf arranged so that where a plurality of signals are governed through a single field station the control code for clearing any one of the signals is transmitted when the route relay in the office for that signal shows that the. route governed thereby is complete, and so that transmission of the control code for clearing a signal actuatesr means in the office for locking the route relay for that signal and does not affect. the route. relays for other signals governed through the same field station.

Another object of the invention is to provide. improved means of the type described which operates so that the. operator is always able. to transmit a control code. to put a. signal to stop or to hold it at stop, andv so that a. control code for this purpose will always be transmitted promptly irrespective of the condition of the route relay or. other apparatus at the office.

Referring. to the accompanying drawings, Fig. 1A shows the operators control panel; Figs. 1B to 1H, inclusive, showthe circuits and apparatus associated therewith at the control of.- iice; Fig. 2A shows a typical track layout chosen to illustrate our invention; Figs. 2B to 2H, inclusive, and Figs.Y 2J and 2K show the wayside/ circuits and apparatus.

Similar reference characters refer to similar. parts in each of the views:

To simplify the circuits, wehave herein shown only the terminals of the sources of current forv energizing the various relays, the reference char-- acter B designating the positive or supply terminal and the reference characterA C thev negative, or common return terminal of the local source. of current, in` each instance.

In some., instances, in order` to simplify the drawings, relay contacts are shown separated.

from the relay winding and Where this is done the relay with which thecontacts are associated,

is indicated by suitable reference characters. placed above the contacts.

To illustrate our invention weV have shown an interlocking control system of a conventional type in which all operations forv the. protection of traffic movements are controlled locally and are governed over a communication system from a central ciilce. Our invention relates principal-- ly to the apparatusV at the central office and.

involves assigning switch and signal controls and indications to the various coding units so that certain units are used' fory the. control and indicationA of track switches only whilev othersv are used forthe control and indications of sig',-r nals only. Starting relay means are provided for each coding unit, there being, a single starting relay for units assigned to the control of' track. switches only., such. asA the relays. 234ST.

and 235S'I of Fig. 1E forithe coding units 234 and 235, respectively, and there being two starting relays, such as relays 2RLST and SRLST of Fig. 1F, for the coding unit controlling two sets of signals, such as the unit 236 which controls a rst group of signals 2BA, ZRB, ZRC, 2LA and 2LB, and a second group of signals SLA, GLB and 6R, shown in Fig. 2A. The invention also involves the provision of a repeater relay for.

each oi the starting relaysfor the -coding units controlling the signals, the repeater relay ZRLSTP of Fig. 1F for the starting relay lRLS'Il being typical. Signal clearing relays, such as ZRGS, provided for each signal control lever and controlled over a conventional route circuit network of Fig. 1B, also are employed.

Each starting relay for the coding units assigned to switch control only, such as the relay 234ST for coding unit 234, is arranged to become energized whenever the starting button for that coding unit, such as button -2313STB of Fig. 1A for unit 234, is actuated, or whenever the starting button for a signal control lever is actuated, provided that the signal lever governs traic over a switch controlled by that coding unitand the control lever for that switch is out of correspondence with the indicated position of the switch. vEach such starting relay is eiective to initiate or store for transmission, a control code from the associated coding unit as soon as such starting relay becomes energized. Each starting relay for the coding units assigned to signal control only, such as relay ZRLST of Fig. 1F, is arranged to become energized when the starting button of the associated signal control lever is actuated to pick up its push button repeater relay, such as the relay 2RPBR of Fig. 1H controlled by the push button of signal lever ZRSG. The starting relay forthe signal control coding unit, when picked up in the manner described, remains energized overa stick circuit until the associated coding unittransmits its code, or until manually released by the operation of a cancelling button C1B.l Each such starting relay when energized prepares a starting circuit shown in Fig. 1F for its associated coding unit, which circuit is completed over a contact closed by the signal lever when reversed, and a contact closed when the signal clearing relay for that` lever is energized.

.Each signal clearing relay, such `as `the relay 2RrS, when energizednot only completes the starting circuit for the associated coding` unit, but also completes the circuit for Vthe repeater relay provided for the associated,starting relay, such as the repeater relay ZRLSTP provided for the-starting relay ZRLST of Fig. 1F. Each repeater relay when picked up in turn completes a stick circuit for thev associated signal clearing relay, this stick circuit serving to hold the signal clearing relay energized independently of the route circuit network. K

At the station the indication coding` units are controlled so as to initiate the transmission of an indication code as soon as a signal clearing code is received, thereby to transmit to the oi'ice either` a signal clear or an approach locked" indication, the receipt of which is utilized to maintain the signal clearing relay at the oiiice energized independently of the route circuits and superseding the stick circuit provided by the repeater relay of the starting relay.

When our invention is used, the operator may set up any of the routes through the interlocking and clear thesignal therefor, byA positioning the switch levers to indicate the course of th route and by reversing the signal lever which governs train movements over the route in the desired direction, and then pressing the starting button forming a part of, or associated with, that signal lever.

When the starting button for a signal lever is operated, it picks up an associated push button y relay which closes contacts in the circuits of the starting relays shown in Figs. 1E and 1F.

For example, if the button for signal lever ZRSG The pushbutton relay ZRPBR, for example,v

when energized picks up the starting relay ZRLST (which together with starting relay GRLST constitute the starting relay means for the coding unit 236 controlling the two groups of signals controlled by the signal levers ZRGB, 2LGS and BLGS, ERGS).

The starting relays for the coding units assigned to switch control only, when picked up complete the usual code initiating circuits over their contacts c (Figure.y 1E) to initiate the transmission of code from the associated coding units,. but the corresponding circuits including contacts c of the signal code starting relay in Fig. 1F is held. open at a contact y' of a signal clearing relay, such as the relay 2RGS governed over the route circuit network of Fig. 1B.

The switch control codes are thus transmitted iirst. The character of the code steps for oper-v ating the switches are controlled over the circuits of Fig. 1C in such a manner that they are effective only if the switches are free to be operated at the time, and not, for example, if the switch is included in a coniiicting route already established. The circuits of Fig. 1C for this purpose correspond generally to the analogous circuits of the Jerome, Lewis and Pascoe prior application, Serial-No. 649,598, hereinbefore'referred to. Y

When the route is fully established as indicated by the operation of the switch indication relays NWK and RWK of Fig. 1C tofcorre'spond with the positions of the switch levers SW, the signal clearing relay of Fig. 1B, such as 2RGS. f

picks up to close its contact :i in Fig. 1F to initiate the code, and also closes a contact h in Fig. 1F to pick up a code indicator or starting relay repeater ZRLSTP, which relay isolates the signal clearing relay from the route circuit net-j work of Fig. 1B and holds it energized until an indication is received of the response of the'signal to its control code.

The character of the signal control steps of this code are goverened by the signal lever and the associated signal clearing relay in the manner shown in Fig. 1D, which circuits also correspond to those of the Jerome, Lewis and Pascoe application, Serial No. 649,598.

The'signal clearing relay ZRGS is held energized by the associated signal indication relay ZRHK which when energized indicates either that the signal is at clear, or if theassociated indication relay 2LHK is also energized, that the" approach or time locking for the signal.' is in. effect, following the manual return of the signal to stop, the wayside circuits for controlling relay ZRHK for Vthis purpose being shown in Fig. 2K. A novel feature of the present case is the addition of contacts of the signal control relays RHS and LHS to the indication control circuits of Fig. 2K, for purposes hereinafter pointed out.

Having thus described the principal features of our invention, we will now describe the system in detail.

The wayside circuits and apparatus As herein disclosed, the apparatus of our invention is represented applied to the control of a typical arrangement of track switches and wayside` signals. The wayside apparatus and circuits are in. general similar to those shown in the aforementioned Jerome et al. application, Serial No. 649,598, with the track layout shown in Fig. 2A being identical with that of the Jerome et al. application, comprising two main tracks of a; double track railroad connected by the crossover switches SAW- 33W and SAW-SBW, the lower track also including two single switches IW and 1W. Main line train movements over the tracks of the layout are governed by the high speed signals 2RA and SLA, and other movements by the slow speed signals2RB, ZRC, ZLA, I

circuit provided with a'normally energized track relay designated by the reference character TR with a numerical prex corresponding to the numerical prefix of itsA associated detector section.

The track switches W are operated -by power operated switch and lock mechanisms SM controlled by polarized switch operating relays WZ, it being understood that each mechanism SM and controlling relay WZ is identified by a prefix corresponding in each case to the prefix` (I, 3A, 3B, etc.) of the associated track switch. Preferably the circuits for the relays `WZ shown in Fig. 2E are arranged to incorporate 'a suitable overload relay OR, as shown, these circuits being arranged as shown and described in .Letters Patent of the United States No. 2,124,601, issued Julyzii,V 1938, to Norman F. Agnew et al., for Railway Switch Controlling Apparatus.

In Fig. 2E, and likewise in other views involving a plurality of similar sets of circuits, only one set of each type is shown in detail.v Thus it is to be understood that the circuits for relay 1WZ, for example, controlling switch 1W, are similar to those shown for relay IWZ, and that those .for the crossover switches SAW-BBW are similar to those .shown for the switches 3AW--3BW- 'Each individual track switch (IW and 1W) and each crossover (3AW, 3BW and 5AW, EBW) is controllable under proper locking conditions as'refiected by the locking relaysLR of Fig. 2J, :by a switch control relay designated by the reference character WSR with a numerical preiix corresponding to the numerical preiix of the associated track switch or crossover. Each WSR relay as shown is of the polar stick type and each vsuch relay replaces the pair of neutral stick relays NWS and RWS provided for the station storage unit of Fig. 8 of the Lewis patent, it being understood that the switch control relays WSR are controlled by codes which reflect the positions of the corresponding switch levers, such as. lever'ISW of' Fig. 1A..

Each switch. SM, together with the associated switch operating and control relays WSR and. WZ, controls a polarized switch indication relay WP, and normal and reverse repeating relays NWP and RWP, shown in Fig. 2F. The circuits of Fig. 2F are arranged as shown and described in Lettersv Patent of the United States No. 2,351,495, issued June 13, 1944, to Arthur E. Dodd, for Electrical Control Apparatus. Each switch repeating relay NWP or RWP when energized indicates that the associated switch or crossover, as the case may be, is locked in the normal or reverse position, respectively', and also that the associated switch operating and control relays are in the corresponding normal or reverse position.. The switch repeating relays NWP and RWP' govern the route circuits of Fig. 2B, the signal circuits of Fig. 2C, the locking circuits of Figs. 2G, 2H and 2J, and also govern the transmission of indications of switch position to the oiiice as shown in Fig. 2K.

Each of the signals of Fig. 2A is to be understood to be. of the well-known searchlight type, having a mechanism conventionally represented in Fig. 2C, and identified by the reference character G, prefixed by the designation of the signal, and controlled over a circuit network conforming to the track layout. The circuits for the mechanisms G are prepared by the energization of route relays, designated by the reference character H with suitably distinguishing prefixes, which are controlled over route circuits shown in Fig. 2B, by the signal control relays HS of Fig. 2D, and by the switch `repeating relays NWP and RWP of Fig. 2F, in such a manner that each route relay 'H becomes energized in responseto the energization of the corresponding signal control relay HS only when each track switch of the route ^governed thereby has assumed a position in agreement with that of its control relay WSR.

As shown in Fig. 21C, the mechanisms ZRAG and SLAG for the high speed signals 2RA and GLA are reversibly controlled by polarized line relays 2RHD and BLHD in a conventional manner to indicate caution or proceed when energized in a normal or reverse direction, and to indicate stop when deenergized. The remaining signals of Fig. 2A govern slow speed movements only, and all their mechanisms are arranged to indicate caution slow speed" when energized and to indicate stop when deenergized.

Each individual signal and each group of signal mechanisms in Fig. 2C controls a conventional stop indication repeating relay designated by the` reference character GP with a suitably distinguishing preiix, which relay as shown in Fig. 2C is arranged to be energized only when its associatedv signal or signals indicate stop. Each signal repeating relay GP together with the associated .route relay H controls a locking stick relay AS shown lin Fig. 2G in a conventional manner such that when any route relay H becomes energized to prepare a signal circuit in Fig. 2C, the ,associated locking stick relay AS of Fig. 2G releases to close its back contact b in the circuit of Fig. .2C prepared by the route relay H for the associated signal mechanism G. Thus for example Vwhen relay 2RH (Fig. 2B) is picked up, its associated locking stick relay ZRAS (Fig. 2G) is released vand back contact b of the latter closes in the circuit (Fig. 2C) prepared by relay 2RH for the group of signal mechanisms ZRAG. ZRBG 1 9 .andrZRCC The circuit for this group of signal mechanisms will be traced in detail hereinafter, but itis to be seen from Fig. 2C that the stop indication repeating relay 2RGP provided for this .group of signal mechanisms is released so long las any ofsuch mechanisms is energized and that relay 2RGP when energized holds open its front contact b in the circuit (Fig. 2G) of locking stick relayv 2RAS so that the latter is released as long as relay 2RGP is released.

The stop indication repeater relays GP (Fig. 2C) `approach or time locking relays AS (Fig. 2G) and signal control relays HS (Fig. 2D) govern the transmission of signal indications by the code system as represented in Fig. 2K, the arrangement being (for al1 signals except 4R) such j' vthat when a relay GP is released, the associated terminal in the eld is deenergized, vand when the'lrelay GP is picked up the associated terminal is energized provided that its associated approach locking relay AS or signal control relay HS is energized. The indications transmitted to the oce on the clearing of a signal result in the K--energization of the associated signal indication relay HK (of Fig. 1D) as will be made clear AsV shown in Fig. 2J, a conventional switch locking relay LR is provided for each switch section and is controlled in the usual manner by l the track relay TR of the same section. Each relay LR, when released, locks the switch or switches in its section by opening its front coni tacts in the circuits for the control and operat- .ing relays WSR and WZ, as shown in Figs. 2D y and 2E. In addition, the conventional section l locking relays ES and WS (Fig. 2H) are employed.

Each locking stick relay AS (Fig. 2G) controls in the conventional manner the circuit for the switch locking relay LR for the rst section of the j route to cause it to release when the locking stick 1 relay releases, andl also releases one or more of the section locking ,relaysA of Fig. 2H to cause the J release of the relays LR for the. succeeding sections oi' the route. For example, if relay` BRAS releases, it in turn releases switch locking relay l-SLR (Fig. 2J)v and section` locking" relay IES .(Fig. 2A). The release of relay- IES .in turn retherefore acts tohold the switch locking relay LR for each section in thekroute releasedfto lock the switches located therein until a train occupy- Aing the route reaches the corresponding section and locks the switches bythe release of the track relay TR thereof.

Returning now to Fig. 2C, it will be seen that the. system operates in the conventional manner so that the clearing of any signal is made dependent` upon the release ofthe associated locking stick relay AS and also upon the locking of the,` switches controlled thereby. The signal circuits (Fig. 2C) prepared by the route relay ZRH, for example, include a back contact b of the locking stick relay ZRAS and also include back contacts of the switch locking relay LR for each f switch of the route. Furthermore, each signal `circuit is connected to the B terminal of the v'source of current over a front contact of the locking stick relay AS for the opposing `signal of v'the same route, thereby providing either time or approach locking protection against the'improper-reversal of the direction of traffic movements. For example, the circuits shown in Fig.

V22C for the group of signal mechanisms 2RAG,

is properly set up and the locking -stick relay for the opposing signal of that route is picked up. Thus, if signal ZRA is to be clearedl for a movement on the lower main track to opposing signal 2LA, mechanism 2RAG gets energy over the previously mentioned contactspof relays ZRH, ZRAS and I-3LR, and is connected toterrninal B over iront contact cof, relay ENWP (connected to the heel of contact f of relay l- 3LR) ,-frontconcontact f vof relay 5,-1LR, and front contact. b

- ofrelay ZLAS. If signal ZRBisto be cleared for `alow speed movement from that-signal tov-either signal 6R or -2LB,l the heel of contai of'relay l---3LRA is connectedto terminal B in thei'lrst case, over front contact f of relay'BLR, front contact h o f yrelay 5NWP or frontcontactl e of relay 2LAS in multiple, and front contact c of relay GLAS; and inthe second case is connected to terminalA Bfoverv f ront contacts c of relays I NWP, 3NWP, SNWP and 1RWP, back contact f of relay 5`1LR andfront contact bof relay ZLAS. If signal ZRC is to -be'CIear-ed, the'heelof contact f of relay. !-3LR is connected through front contact c of relay IRWP to terminal; B at front contact e of relay GLAS over. a circuit previously traced if crossover BAW- BBW is reversed; and

to terminalV B at front contact if the crossover is normal.

b' offrelay 2LAS Each of the signals, as shown, is arranged to -be put to stop automatically when a train. enters the nrst track section of its route, remaining` at stop after the vfirst section is vacated, due tothe vrelease of the associated signal control relay AI-IS shown in FigfZD by contact a of the corresponding track relay TR, the signal-control relayupon releasing causing the corresponding route-relay Hof Fig. 2B 'to release to open-the signal circuit 0`f-Fig. 2C.- `.Under the 'conditions assumed, the

storage relay TS also Ashown in Fig. 2K.. Relay TS is picked "up when the track relay releases and controls vthe transmissiono'f the indication Vcode by which the track indication relay TK'is energized to light a lamp TKE on the track diagram at the oiiice toindicate the occupancyjof the controlling track section, and is held energized to insure the transmission of thetrack occupied indication even though the section isi/acated before the system has anl opportunity to transmit the indication," as explained in the Lewis patent. vWhen the track occupied indication" is transmitted, the associated relay V picksnp'f'in the manner explained in theLewis patent fto interruptthe circuit of the relay TSA and it releases to close its back contact b in the'circuit of the signal control relay. Accordinglyafter a not be cleared again by the transmissionff a signalv clearing code until an indication is transvis vacated.

Energization of a track indication relay TK at the-cnice is accompanied by energization of an auxiliary or slotting `relay TKA (Fie. 1D) which -thereupon remains energized untilV the vassociated Vsignal lever is `restored to its normal position. Each auxiliary or slotting relay is energized upon energization of the associated track indication relay TK only when a route relay for a'signal governing entrance of trafiic into that section v-ispicked up `sovthat a signal clear control code could be transmitted unless prevented by the lBlottingl relay. Each Vauxiliary or Vslotting relay when energized -interrupts the circuits governing 4transmission of control codes for clearing the -associated signal. As a result after a signal has vbeen-'put to stop by lpassage of atrain and an vindication-of occupancy of the section in advance ofthe -signalhasbeen transmitted to the oiiice, a control code for reclearingthe signal will not vbe transmitted until the operator restores the sig- Vnallever to normalV to release the associated V'slott'ingor auxiliary relay. This arrangement 4prevents inadvertent reclearing oi.' a signal'wh'ich hold 'openthe icircuits for the-.associated section 'locking relays and .switch locking relay LR for the-switches vfarther oninathe route, until. that 'first detector section is vacated, each. track relay 'locking thetrackfswitch in its associated detector section through the associated locking relav LR.

v`until .the correspondingsection .is vacated,`to -provide the usualffsectionalrelease ofswitch locking. ,For example, ii after signal 2RA has been "cleared, it is put to'stop by a train entering section IT, 'relay ITR releasesV and closes its back `contacte to pick up relay ZRAS (Fig. 2G) Front :contacts aand` fof relay ITR arenow open and hold open the circuits of relays IES (Fig.v 2H) Vand I-3LR (Fig. 2J). Relay IES holds its front contact :c open in theV circuit oi' relay 5--lLR (Fig' 2J VWhen a track relay releases, its associated track stick relay `TS (Fig. 2K) picks up and in Fig. 2D, it will be-noted that a back contact c of thetrack storage relay TS above referred to is included yin the'circuit of the switch control relay WSR for each switch in the corresponding section, that is, the circuit ofA relay I WSR includes back contact c of relay ITS, and that of relay YIlVSlRrincludes back contacts c of relays ITS and 3TS. These contacts serve to prevent the :receptionnfthe switch .control elements of "a code Whilezthe switch section is occupied,.prior"tothe :transmission vof .an indication ofy its .occupany 'to the o'iiice. VAftertheftrack'.occupied indication istransmitted, rthe transmission of code elements for changing the position of a switch located in an` occupied trackisection is prevented by the opening ofthe back contacts c and d of the track indicationrelays TK, in the circuits of Fig. 1C.

Thearra'ngement'of'the wayside apparatus and circuits of our system 'is substantially similar in many respects to the corresponding apparatus of the Jerome et al. application, Serial No. 649,598, diiering therefrom largely in the organization of the apparatus shown in Fig. 2D for delivering the control codes, and 'inthe apparatus shown in lFig. 2K fortransmitting indication codes. In `accordance withour'invention, the controlcodes and indications are' assigned tothe various code storage units so that certain units control and vindicate trackswitches only, while other units 'control signals only and (in one case) indicate yonly signals or (in 'another case) indicate both signals and track occupancy. Referring to Fig. 2D, it will be seen that unit 234 controls switch control `relays `IWSR- and 3WSR; unit V235 controls switchcontrol relays 'SWSRV and '1WSR; unit 236 controls signal control relays SRHS, SLHS, ZRHS, `and ZLHS; and unit 231 controls signal control Arelay ARI-IS. A corresponding arrangementis shownV in Fig. 2K for the indication codes, Ythe unit 234 indicating the positions of the points of switch IW and crossover .3AW-3BW; thevunit 235 indicating the positions ofthe points .of the crossover 5AW--5BW and switchW; unit 236indicating the signals ,governed .bysignal control relays ..2RHS, ZLHS, 6RHS, AtLHS; and the unit 23T indicating the signal controlled by relay IIRHS, and also indicating-the detector track .sections IT, 3T, 5T,

V.and "IT, 'The apparatus .of Fig. 2K is further arranged in a novel manner so that the circuits for the units 236 and 231 vinclude contacts of the signal control relays HS, whereby each of such units vis caused to transmit a code immediately .when a signal` clearing code has been received by such unit.

The codeY communication system It has alreadybeen pointed out that the centralized trafic control system of our invention may employ the code system of Patent No. 2,229,249, of whichl the field storage units are illustrated in part in Figs. 2D and 2K. For an understanding of our invention, it is deemed sumcientto point out that the communication system may be arranged to provide a plurality, such as seven, code steps or channels, for the intermittent transmission of controls from the omce to a selected storage unit in the field, as well as a similar number of other channels for the transmission of indications from any of the eld storage units to the office.

This system makes use of four channels in the transmission of control codes from the oice to the field stations, and of've channels in the transmission of indication codes from the eld Vstations tothe oilice.A To facilitate understandfsame numberswat both the cnice and eld stations, and the numbers employed for this purpose are a combination of the numbers employed in Figs. 7 and 5 of the Lewis patent to designate the corresponding wires at the oice and'eld stations. For example, in the Lewis patent the .first `control channel is governed by wire IUI at .13 the ofce and governs the controlled relay at the field station over wire 3|, and in this application the corresponding Wires at both the ofce and field stations are designated IUI-3l. The other control channels are designated H13-32, I 92-34, and Mld-35, andthe indication channels are designated in Figs. 1C, 1D and 2K by the numbers IUS-3S, IIB- 40, III-4I, II3--43,

vand I5-45.

For simplicity, the lcode channels are represented herein by direct wire connections, such as would be used for thev control and indication ofv apparatus in the vicinity of the control oillce, although the coding apparatus establishes the channels only one at a time over a single line circuit, but this may be disregarded and the operation may be more readily traced byl assuming that terminals or wires IDI-3l, ID3-32, HB2-34 and M14-35 inFigs. lCand 1D, extend directly to the corresponding wires or terminals in Fig. 2D, and that terminals or wires IUS-39, I Ill-'40,

`III--II, vH11-43 and II--45 in Fig. 2K extend directly to the corresponding terminals or wires in Figs. 1C and 1D.

Each control code transmitted from the oiiice isinitiated by the energization of a starting relay .of which one or more is provided in each oiiice storage unit. Each starting relay may be energized by the operation of a starting button in the corresponding panel, and, when energized, prepares a starting circuit to effect the in1tiat1on of the corresponding code as described in Patent As hereinafter explained in detail, the oice storage unit employed in the control of the signals 2R, 2L, 6R andSL is governed by two starting* 'relays which are designated ZRLST and BRLST,

and either of these starting relaysis capable of initiating transmission of a code by this unit,

Each control code includes a distinctive code -I02-34 and Hill-35 to position a particular group of control relays at the station inv accordance with the condition of energization of the control channelsqas determined by the po- -sitions of the levers of the corresponding office panel. The manner in which the various functions have been assigned to the different code v steps or channels and to the different panels and storage units will be obvious from a considera- -tion of Figs. 1C, 1D and 2D.

In the code system of Patent No. 2,229,249,

the indication codes are initiated by the energization of a normally deenergized starting relay, not shown, in the station storage unit.

vEach starting relay is energized in response to a change in position of any of the indicating relays which govern the unit, and also when the ldelivery relay is operated by a control code. A

return indication code therefore follows each control code. regardless of whether or not the positions of the controlled devices are changed. 'Each indication code includes a distinctive code VVcall'by 'which a selector relay, not shown, and z a repeating relay, such as relay 234MSP, Fig. 2K,

in the station storage unit, and also a delivery relay, such as 234D, Fig. 1C, inthe corresponding oflice storage unit, are energized to establish the indication channels. and Vthereby `effect the selective energi'fation 'of theindication stick -relays INWK. IRWK, etc. of the oice unit in .accordance 'with' the condition of. energization of -the channels as reiiected by the positions of the indicating relays assigned to the corresponding station storage unit. Y

At the end of the code a relay VC, notshown, in the station unit is energized, and connects a series of stick relays IllV, IIV, etc., to the corresponding channels, etc., as shown and de- The circuits and apparatus at the control oice It is to be understood that the system includes the oflice coding and storage units of Patent No. 2,229,249 and that thes'efunction as described in the patent except for 'such modifications as are pointed out herein.

As shown in Fig. 1A, the operators control board includes an illuminated diagram of the track layout and employs four oiilce storage units. One storage unit is assigned to the control ofv switch IW and the crossover switches 3AW and 3BW, another to the control'of the switch 'IW and the crossover switches 5AW and SBW, the third to the control of signals 2RA, ZRB, ZRC, 2LA, 2LB, 6R, SLA and SLB, and the vfourthto the control of signal 4R. A signal control lever, preferably oi the type incorporating a starting' button, is provided for each of the following groups of signals, 2BA, ZRB, andv ZRC; 2LA and 2LB; GLA and SLB; and for eachr of the single signals 6R and 4R. Each signal control lever is designated-by the reference charac- .ter SG, with a suitably distinguishing prefix and 1E, designated by the reference character ST with the numerical prei-lx corresponding to the code call of that unit. The coding unit assigned to the control of the signals ZRA, ZRB, ZRC, 2LA, ZLB. ER, GNRA, and RB is provided with two starting relays, Fig. 1F, designated ZRLST and BRLST. The other coding unit assigned to the vcontrol oi signal 4R is provided with a starting relay, Fig. 1F, designated IIRST.

Fig. 1G shows the circuits for the lampsk associated with the signal levers ZRSG and ZLSG, and with the switch lever ISW, and also the circuit-for the lamp ITKE which indicates occupancy of section IT. It is to be understood that the circuits, not shown, for the remaining indication lamps on the operators control board are similarly arranged.

The starting buttons associated with the`signal levers each control a slow release repeating relay PBR, Fig. 1H, the purpose of which is to provide a larger number of contacts than it is practicable to provide on the startingl button. Each relay PBR, when energized momentarily,

.controls circuits in Fig. 1F to energize the sigliever: In case the'k establishment ot ai mutereq'uires a;` change in; thepo'sition of one- 'or more of the traclf` switches, the operated. relay PBR completes circuits; in; Fig.A 1E, to. pick 'up the starting relays ST which initiate codes for-operatingfth'ev track. switches, thereby storing codes for op'eratingthe switches as required, in addition tol storing a code forclearing the signal for the route, in. response to a.y single operationv of 'the starting button associated vwith the operated signallever SG.

'Reterring'to Eig..1E, the starting relays 234ST and 235ST correspond. to those designated 234 andZGS' inFigs. '2" and 5 o'f Patent 2,229,249, and the circuits in Fig. 1E controlledover` contacts -c of the relays ST correspond to those shown in Fig; 2' of the patent. A

The starting relays' 2RLST. and SRLST, Fig. 1F, which-initiate the transmission of control codes for governing the signals 2L, 2R, 5L. and 6R; together correspond to the starting `relay 236 of Fig. 2' of 'the Lewis-patent, while the starting 'relay 4RST 'which initiates transmission of 'control codesv for governing the signal 4R, cor- 'ie's'pondsto theA starting relay 23'! of Fig'. 2 of the Lewis patent; The circuits governed over contacts c of'these starting relays correspond to those in v2 ofthe patent' except for the addition ofn'ovel means hereinafter described arranged in accordance with our invention for controlling4 these circuits to defer transmission oi.' a signal control code until predetermined conditions exist.

It' is to be understood that thes'e circuits normally' function as described in 'the patent, nam'el'y, when one ormore of the contacts c of the starting relays ST are closed and connected to 'terminal B, 'and the code line circuit `is free, the coding unit becomes energized to initiate the transmission of a control code including selecting elements comprising a code call by which a selector relay, such as relay 234s, at the oiiice is "energized, together with a delivery relay F234D at the selected station. The energization of the selector relay l234sy prepares a circuit by which the associated starting relay 234ST is released by the code system relay O8 when the code call portion of the control code is fully transmitted.

ln accordance 'with our invention', each ofthe startiz'igrelays` governing 'transmission of a signal control code, such 'as 'relay ZRLST, Yshown in Figi 1F, governs a repeater 'relay STP which i's picked up 'when the associated starting' relay ST becomes effective 'to transmit 'a code for clearing a signal, and then is held energized until an indication code is 'received from the station storage unit through which indications of the condition of the controlled signal are transmitted to' the' oiiice'. Each relay STP is released by the 'operation ofthe delivery relay D of the associated'oiiice storage unit, such as the relay 236D, which relay, as shown in Fig'. 5 of the patent and in Fig. 1D of the accompanying drawings, alsov operates the cilice signal indication relays ZRHK', 2LHK, etc., in' accordance with the conditions of the signals and associated signal control relays.

The transmission of control codes for' governlng the tract; switches is governed by 'the switch indication relays of- Fig. 1C as well as by thev switch control levers, and referring to Figs. 1C and 2K. it'willv be seen that 'the relavs INWK and IRWK are normal and reverse switch indication relavs which reect the position of the corresponding track switch IW and of the con- 16 trol. and operating relays IWR and. IWZ` therefor; Each. normal or. reverse switch indication -relayisadapted to be pickedup by code over the associated indicationchannel, and is held energized. locally after the termination of the code by a. stick circuit extending from terminalB at its front contact a, over a back contact of the delivery relay, and through the relay winding to terminal C at contact b or d of the associated switch lever., such as lever ISW, provided the lever position corresponds with the indicated position of the switch. If the switch lever is movedv to its opposite position, the circuit for the energized indication relay is extended to include back contact d or e of the associated code starting relay, such as relay 2'34ST, so that when the starting relay is. operated to initiatev a code for changing the position of the switch, the energized indication relay is released to cancel the switch indication. Thus the normal indication `relay NWK is released by a switch reverse control code, and the reverse indication relay RWK by' a switch normal control code.

This control of the transmission of the control codes fortrack switches is explained' in detail in application Serial No. 649,598 of Arthur L. Jerome, Lloyd V. Lewis and Frank T. Pascoe, wherein it is pointed out that when a starting relay is picked up, the connection to terminal C of each. of the indication relays for the switches governed by that starting relay is governed by iront contacts' of the route check relays RGS or LGS of Fig. 1B, by means of which the energized indication relays for the switches of'a Vvroute are held energized over'the front contacts ci cr e of the starting relays 234ST, etc., while control codes are stored for transmission or are being" transmitted. These circuits serve to 'prevent the release of the switch indication relays if` an attempt is made to voperate any switch included in an established route when the route check' relay RGS or LGS for the signal governing traiiic movements over such rou'te is energized.

In Fig. 1C, back contacts c of the switch indication relays are included in the circuits over which the switch control channels IUI-3|, H12-34, H13-32, and IUI-35 are energized in accordance with the positions of the contacts a of the switch levers, so Vthat cancellation of the switch indication is necessary in order to render the switch. control elements of a code ei.'- fective' to ch'ange the position of the switch control. `relay WSR, Fig; 2D, which such elements govern. Otherwise both channels for governing a switch control relay are deenergized in a code transmitted when a switch lever and its control relay'WSR occupy dissimilar positions, and relay WSR is not operated.

Referring now to Fig. 1B. it' will be seen that front contacts b and d of the switch indication relays together' with contacts oi' the switch levers are so interconnected that when closed they form route circuits, there being' one 'such circuit 'conforming'to each route through the track layout' of Fig. 2A. It will also be seen that when any signal' le'ver', such 'as lever ZRSG, is operated to its reverse position, with a route circuit established, the corresponding rou'te check relay 2RG'S -is' connected to the route circuit over the 'signal lever contact e or f and becomes energized and in turn holds energized the switch indication' relays for the switches of the corresponding' route. It follows that the energization of a control channel 'to operate a track switchv `away from its existing position is pos- 17 sibleonly when the route check relay jfrorv each route over the switch is released.

Visual indications of the conditionv of the switch indication relays are provided in the control board of Fig. 1A by lamps such as INE and IRE mounted above the switch levers and energized over contacts e of the indication relays as shown in-Fig. 1G. Y

Considering now the remaining indication relays of Fig. 1D, the relays ITK, 3TK, etc. are track indication relays controlled through station 231 to light red lamps ITKE, etc., in the track diagram, to indicate when the corresponding track sections are occupied, the lamp circuits being shown in Fig. 1G. Storage ofthe detector section lindications is provided, and when, forexample, the track relay ITR of Fig. 2K releases, an indication of occupancy of the section is stored by relay ITS, as described in Patent No. 2,229,249.

It has already been explained that code elements effective to operate a track switch are transmitted only when each route check relay, such as relay ZRGS or 2LGS of Fig. 1B, which governs a route over the switch, is in itsV released position, and' that each such route check relay becomes energized in'response to the reversal of the associated signal lever ZRGS or 2LSG, provided a route circuit is established in Fig, 1B, for agroute governed by a signal which such lever controls. If the route check relay becomesjenergized, a signal clearing code may be initiated lby operating the associated startingv button, or as hereinafter explained, is automatically initiated in accordance with our invention upon picking upof the route relay if the starting button had previously been operated to pick up the signal starting relay. When a route check relay picks up and the associated startingrelay is picked up, a repeater relay STP (Fig. 1F) is energized and this repeater relay STP then disconnects the energizedfroute check relay from the route circuit but holds it energized over a 'stick circuit, as shown in Fig. 1B.

when signal iever RSG is moved to the right and the control code to clear signal- 2R istransmitted,- wire H12-34 is connected to terminal B as shown in Fig. 1D, over the right-hand contact a of lever ZRSG, back contact a. of a'relay ITKA, previously described, and front contactfd of relay ZRGS, causing the signal control relay 2RHS of Fig. 2D to pick up. Thiscode is of. course ltransmitted only after the route relayin the oiice indicates thatwa route is available at the station, and consequently when relay 2RHS picks up, it completes a circuit for relay 2RH (Fig.r 2B) which picks up to close its contacts a, and e, to prepare the circuit (Fig. 2C) for the group of signal mechanisms ZRAG, 2RBG Aor ZRCG. Relay ZRH also opens its Vcontact b in the circuit (Fig. 2G) for relay ZRAS, and the-latter relay releases to open the circuits for relay IES (Fig. 2H) and relay VI,-'3LR (Fig. 2J). With relay ZRH picked up and relays ZRAS and I-SLR releasedfthe circuit networkis completed vover which the proper signal mechanism ZRAG, ZRBG or'ZRCG, as selected by relays vZRHD andVV IRWP (Fig. 2C) is supplied with energy over a circuit 4path determined by the route set up and hereinoice relay ZRHK picks up (Fig. 1D) and closes itsV contact a in the circuit (Fig. 1B) of relay ZRGS to maintain that relay energized over its stick circuit after relay ZRLSTP releases. Relay 2LHK may also pick up at the ofElce atthis time, depending upon whether terminal I09--3'9'at the station is energized or not, and it follows that if relay ZRHS picks up, its front contact e, Fig. 2K. establishes circuits for controlling the channels IUS-39 and I I I-4I so that the return indication code is certain to indicate either the clear or the approach locked condition Vof the signal `by ener-.- gizing vrelay '2RHK alone or along withv relay The approach locking relay ZRAS also controls a circuit over its front contact e (Fig. 2K) `for supplying energy to channel III-4I over vwhich relay ZRHKis controlled so that after release of relay ZRHS the indication codesI transmitted to the oice maintain the'relay 2RHK picked up as long as the relay ZRAS is released. Y.

Itfwill be seen, therefore, thatl after .a signal clearing code for energizing a, signal control-relay, such as ZRHS, has been stored for transmission, the route check relay ZRGS is locked energized, and can be released only after an indication code has been received which indicates that relay ZRHS has been released and the approach locking relay ZRAS is picked up. The route Scheck relay ZRGS, when energized', maintains the route circuit established by reason of its control of the stick circuits for the switch indication relays Yin Fig. 1C, to 'prevent a change in route, and is releasable only when itis proper to change'the route, since the code which indicates that the signal control relay ZRHS is released must also indicate that the signals such relay controls'are at stop and that their approach locking relay' ZRAS is energized before the relay ZRHK is re`- leased to interrupt the stick circuit for relay ZRGS. f

Assuming thatv relay ZRHS has been picked up bythe .energiz'ation of channel I0234, to clear one of the' signals which relay ZRHS controls, for an approaching train, if lever ZRSG isnot moved from its right-hand position, channel I02.-'34 will be energized over the previously traced circuit including contact a of lever ZRSG in its rightliand position (Fig. 1D) in each succeeding code transmitted by the same unit prior to the time the train enters section IT, thereby maintaining relay 2RHS picked up to hold the signal at clear until the train passes it.

Under the conditions assumed i. e. With one of the signals controlled by relay ZRT-IS cleared,when the train enters section IT, relay ITR releases to initiatethe transmission of a' track occupied indicationcode, as already described, whilerelay ITSl is picked up. to lstore the occupied indication if the section shouldbecome vacated :before that in' dication is transmitted to the oflice. When relay ITR releases, its contact b, Fig. 2K, interrupts the circuit of the slow release repeater relay I TP and after a short time interval relay ITP releases so that its back contact a in the circuit of relay ZRHS (Fig. 2D) is closed and so that front contact b of relay I'IP in the pick-up circuit of relay ITSA (Fig. 2K) is open. In the period after re" lease of the relay I TR and prior to release :of the relay ITP, the circuit of relay ZRHS is interrupted and it releases tointerrupt its stick circuit so that it remains released after back contact va ofv relay ITP closes In addition, in the period after' release of relay ITR and prior to release of relay TPfenergy is supplied to relay ITSA over its.-

When the indication code including the track.

occupied indication is transmitted, relay ITK at .the oflice becomes energized to light Vlamp ITKE (Fig. 1G). When relay ITK is first. energized, a circuit is closed momentarily .from channel IIB-45, Fig. 1D, over back contact bv of relay ITK and Afront contact g of relay 2RGS through the upper winding of relay I'-I.TKA. to terminal C. Relayy `I.-.'ITKA, therefore; picks up and establishes a'. sticlrcircuit including its frontcontact a and contact a of lever ZRSG in its right-hand'v position and relay I-'-'ITKA,re mains energized until lever ZRSG is restored to normal. Relay ITSA is released upon the transmission. of the track occupied code, ren-` dering relay 2RHS responsive to control codesin which channel H12- 34? is energized.'V It iol'- lows that the energization of a signal control f channel in a transmitted code cannot occur inadvertently, due to a failure vof the. operator to. return the signal lever' to normal after the signal it controls hasbeen put to stop by a train.'

Operation The operation of the system of our invention under diierentv assumed conditions will now be described, starting with the apparatus in. the condition shown in the drawings, with all switches normal, all signals at stop, and the detector track sections unoccupied.

Starting with this apparatus inv its lnormal condition; as shown, it will be first assumed that` the operator reverses the switch lever SSW tov reverse the crossover switches 3AW-3BW, and that he then moves the signal lever ZRSG to the right and presses Ythe associated starting button to clear signal 2RB, for a train movement over that route..

The operation of the starting button associated with lever 2RSG energizes'the relay 2RPBR, Fig. 1H, thereby energizing relay 234ST over the circuit shown in Fig. .1E and including front contact a of relay ZRPBR, reverse contact c of lever SSW, back contact f of vrelay SRWK, and a back contact of starting button 234STB, to initiate the transmission ofa control code to` station 234 to operate crossover 'switches SAW-313W. The :opening of back contacte eof. relay 2,34ST, Fig. 1C, releases relay'3NWK and by the resulting code, relay 234s, Fig. IC', is energized to connect terminal B over back contact c of relay 3TK' and back contact d of' relay ITK at Contact d of relay 234s over the reverse contact a of the switchV lever v3SW and back contact c of` relay 3NWK to channel IIN-35, and in Fig; 2D, the delivery relay F'ZMD- is energizeo.v to extend channel IDA-35 over contact d of relay F234D through the lower winding of relay 3WSR to terminal C over front contacts e oi'Y the switch locking relays I--3LR and 3LR and back contacts cI oi the track storage relays ITS. and 3TS provided the proper traflic conditionsv prevail as manifested bythe energization 20 of theseA locking. relays and release oiv the track storage relays.

It will bev seen that when switch lever 3SW is reversed,v its contact' h opens the route circuit in Fig.1B for the existing route from signal' 2R` to 2L, while this circuit is additionally interrupted on release of contact d of relay SNWK. and that the operation of the interlocked circuits of Figs. 1B and 1C isy such as to require the switch and signal levers and starting buttons to be operated in the sequence recited above. Thusrif signal lever ZRSG is reversed and the associated starting button is pressedy before the` switch leverSSW is reversed. relay ZRGS, Fig'.` 1B, will -be energized over the route circuit extending to terminal B at back contact a of relay ZLGS, while the relay ZRLSTP (Fig. IF)- willbe energized and its contact a will remove relay ZRGS from the network and' will.l establish a stick circuit to maintain relay ZRGS energized. If, after picking up of relay 2RGS, the operator should then-press button ZMS-TB after reversing leverv 38W, the energization of relay :MST wouldv complete a circuit in Fig. 3C from the left-hand terminal of the winding of relay 3NWK,-fover -contact b of lever BSW, frontV contact eof relay 234ST; over back contacts e of relays 4RGS,J SLGS and ZLGS, tov terminal C at front contact e of relay ZRGS', holding relay BNWK energized 'to maintain channel IIN- 35 deenergized inthe transmitted code, so that relay 3WSR.y would not be operated to reverse.

The operator, however, may move lever ZRSG to the right after lever SSW is reversed or relay l BNWK releases, but relay Z'RGS will remain released until the new route is established and' indicated. During this period channel H12-34, Fig. 1D, is disconnected from contact a of lever ZRSG bythe open contact d of relay ZRGS'. and relay ZRHS would remain released in the eventl a control code should be transmitted from oflice storage unit 236.

Since relay INWK is held energized over the normal rcontact b of lever ISW, it does not release-whenv relay 234SI picks' up. It follows that the operator is free to initiate a control code by operating relay 234ST to control any appropriate function over any of the idle channels in this storage unit, and that this function may be governed independently of the switch levers assignedto the same unit.

' When lever 2RSG is reversed and the asso ciated starting button is pressed to pick up relay ZRPBR, contact b of relay ZRPBR, Fig. 1F, establishes a pick-up circuit for relay ZRLST and its contacts pick up to establish a stick circuit forj'the relay. In addition, when relay 2RLST-picks vup, its contacts c and d prepare circuitsY for the relays OM and 2RLSTP, but these-circuits are not complete until relay ZRGS picks up. As thel circuit of relay OM is not complete on picking up of relay ZRLST, the relay ZRLST is ineffective at this time to control relay OM to initiate operation of the oilice coding unit to transmit a control code.

As is shown in Fig. 1G, when relay ZRLST picksup with lever 2RSG reversed, energy is supplied' over contact b of relay 2RLST to lamp ZRE through a resistor so this lamp is lighted dimly. At this time lamp 2NRE continues to be lighted overthecircuit including back contact c of relay 2RHK and thev dim lighting of lamp ZRE along with the lighting of lamp ZNRE provides a distinctive indication of the fact that a control for clearing signal 2R has been initiated, but 

